package com.open.common.persistence.dialect.db;

import com.open.common.persistence.dialect.Dialect;

/**
 * A dialect compatible with the H2 database.
 */
public class H2Dialect implements Dialect {

	public boolean supportsLimit() {
		return true;
	}

	/**
	 * 将sql变成分页sql语句,提供将offset及limit使用占位符号(placeholder)替换.
	 * 
	 * <pre>
	 * 如mysql
	 * dialect.getLimitString("select * from user", 12, ":offset",0,":limit") 将返回
	 * select * from user limit :offset,:limit
	 * </pre>
	 *
	 * @param sql 实际SQL语句
	 * @param offset 分页开始纪录条数
	 * @param offsetPlaceholder 分页开始纪录条数－占位符号
	 * @param limit 分页每页显示纪录条数
	 * @param limitPlaceholder 分页纪录条数占位符号
	 * @return 包含占位符的分页sql
	 */
	private String getLimitString(String sql, int offset, String offsetPlaceholder, int limit, String limitPlaceholder) {
		return sql + ((offset > 0) ? " limit " + limitPlaceholder + " offset " + offsetPlaceholder : " limit " + limitPlaceholder);
	}

	@Override
	public String getLimitString(String sql, int offset, int limit) {
		return getLimitString(sql, offset, Integer.toString(offset), limit, Integer.toString(limit));
	}
}